[Milsurplus] Aircraft electrical system question

[WA5CAB at cs.com]

Jim,

In answer to your first question, as previously stated, in the LV DC 
systems (either 12V or 24V),.one of the battery terminals was grounded near the 
battery.  In US practice, with all but two vehicular sets (that I can think 
of) of what are commonly considered WW-II vintage equipment  (SCR-284 and 
TCS), this was the negative terminal.  What the British did I don't know.  At 
least in ground vehicles (specifically the Land Rover, which is post war), the 
vehicles were still positive ground into the early 1960's.  But in any 
case, But in any case, all of the US WW-II vintage ground and aircraft radios 
will work with a negative ground on the LV side.

I don't know the answer on 3-phase 400 CPS inverters as all of the examples 
I've ever had anything to do with have been single phase except for a 
couple of very small inverters that were used with only one dedicated load.

I would suggest that you go ahead as a matter of course and remove the 
internal -12V ground in all of the supplies that you buy.  And only ground the 
-24V terminal external to the actual supplies.  That way, if you should ever 
have to replace one of them, it won't matter which one you are replacing.  
Your spare(s) will work for either one.

In a message dated 12/20/2015 10:18:22 AM Central Standard Time, 
antqradio at sbcglobal.net writes: 
> Was one of the 24 volt aircraft battery terminals grounded to the frame 
> as in cars?  Same question applies to the 115 volt, 400 cycle three phase 
> distribution system, was one leg grounded through a center tap on one stator 
> winding?
> 
> 
> I am setting up a 24 power supply using 12 volt router power supplies.  
> They are pretty cheap on eBay, going for $10 or less for 400 to 1800 watt 
> examples and that is including shipping.  In the particular supplies I have, 
> the negative 12 volt terminal is grounded to the 60 cycle AC plug ground 
> terminal.  I have already removed the ground on one power supply so that it an 
> be stacked to get 24 volts and wonder if I should do the same to the other 
> so that the 24 volt supply is floating with respect to 60 cycle power 
> ground.  Thoughts?
> Jim
> 
> 

Robert Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480
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